It is often argued that bottom-up causation under a physicalist, reductionist worldview precludes free will in the libertarian sense. On the one hand, the paradigm of classical mechanics makes determinism inescapable, while on the other, the leading models that allow a role for quantum effects are noncommittal regarding how conscious agents are supposed to translate indeterminacy into self-formed choice. Recent developments, however, not only imply that self-formed decisions are possible, but actually suggest how they might come about. The cornerstone appears to be causality superposition rather than quantum-state entanglement, as is usually assumed, and the natural arena for applying these developments is (perhaps ironically) a framework that was built without any consideration for quantum effects.
It is often argued that bottom-up causation under a physicalist, reductionist worldview precludes free will in the libertarian sense. On the one hand, the paradigm of classical mechanics makes determinism inescapable, while on the other, the leading models that allow a role for quantum effects are noncommittal regarding how conscious agents are supposed to translate indeterminacy into self-formed choice. Recent developments, however, not only imply that self-formed decisions are possible, but actually suggest how they might come about. The cornerstone appears to be causality superposition rather than quantum-state entanglement, as is usually assumed, and the natural arena for applying these developments is (perhaps ironically) a framework that was built without any consideration for quantum effects.
Abstract Advancements in neuroscience make the question of free will more pressing. Between physicalist positions, which largely deny free will, and libertarian views, which reject determinism, quantum mechanics initially appeared to offer a middle ground. Even though it was thought to depict a probabilistic reality allowing some degree of freedom in choices, quantum mechanics remains deterministic, albeit with stochastic results. This paper proposes an alternative where quantum mechanics still supports free will as the possibility to do otherwise within a physicalist framework. Through the manyworlds interpretation, I show how the principle of alternative possibilities can be maintained, even when both our decision-making processes and the external world follow physical laws.
In the libertarian ``agent causation'' view of free will, free choices are attributable only to the choosing agent, as opposed to a specific cause or causes outside the agent. An often-repeated claim in the philosophical literature on free will is that agent causation necessarily implies lawlessness, and is therefore ``antiscientific." That claim is critiqued and it is argued, on the contrary, that the volitional powers of a free agent need not be viewed as anomic, specifically with regard to the quantum statistical law (the Born Rule). Assumptions about the role and nature of causation, taken as bearing on volitional agency, are examined and found inadequate to the task. Finally, it is suggested that quantum theory may constitute precisely the sort of theory required for a nomic grounding of libertarian free will.
In the previous chapter, we saw that rather than thinking about reality as a static state, it may be helpful to think of it as a process, and perhaps even a process in which the observer participates: she has an active role in determining what is observed. This is certainly true in quantum physics, where quantum superposition is not resolved until a measurement is made. Our classical way of viewing the world leads us to interpret it as being much more absolute at the (larger) scale at which we live our lives. But, as we saw in Chapter 4, quantum processes play much more of a role in our daily lives than we typically realise. For example, entanglement, where two quantum systems interact immediately irrespective of their distance, is a central concept in quantum physics. Yet it appears to defy causality, as we are used to defining it (where one event causing another must always precede it). Erik Verlinde said the following about quantum entanglement:
The nature of emergence of complexity out of the underlying physics is a key issue in understanding the world around us (1). Genuine emergence can be claimed (2⇓–4) to depend on top-down causation, which enables higher emergent levels to direct the outcomes of causation at lower levels to fulfill higher-level causal requirements; for example, the needs of heart physiology at the systems level determine gene expression at the cellular level via gene regulatory networks (5) (Fig. 1). However, the idea of top-down causation has been denied by a number of commentators (e.g., refs. 6 and 7). The paper by Aharonov et al. (8) makes a strong contribution to this debate by giving quantum physics examples where top-down causation manifestly occurs. This physics result has strong implications for the philosophical debate about whether strong emergence is possible. Indeed, it gives specific examples where it occurs in a remarkably strong form.
Fig. 1.
Bottom-up and top-down causation from the quantum level up to the organism level and down again. Adapted with permission of Royal Society, from ref. 5; permission conveyed through Copyright Clearance Center, Inc.
Now, the word “causation” is regarded with suspicion by many philosophers of science, so to characterize what is happening one can perhaps rather use a number of different descriptions such as “whole–part constraint” or “top-down realization.” The key point remains the same, that higher levels can influence lower-level outcomes in many ways, and hence explain how strong emergence is possible. This occurs across science in general, and in physics in particular (3, 4). The latter point …
[↵][1]1Email: george.ellis{at}uct.ac.za.
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The basic question in the long-standing debate about free will (FW) is not whether FW can be demonstrated to exist nor even whether it exists, but instead how to define it scientifically. If FW is not dismissed as an illusion nor identified with a variety of unpredictability, then logical paradoxes arise that make FW elusive to define. We resolve these paradoxes through a model of FW, in which FW is a new causal primitive empowered to override physical causality under guidance. We develop a simple mathematical realization of this model, that when applied to quantum theory, suggests that the exercise of FW corresponds to a nonlinear POVM causing deviations from the Born rule. In principle, these deviations would stand in conflict with known conservation laws and invariance principles, implying that the brain, the presumed seat of FW, may be an arena of exotic, non-standard physics. However, in practice it will be difficult to distinguish these deviations from quantum and neural noise, and statistical fluctuations. We indicate possible neurobiological and neurological tests, implications and applications of our proposed model.
Our discussion in the first five sections shows that little new can be said about compatibilism, that van Inwagen's argument for incompatibilism still stands, and that the view of free agency for a libertarian has little chance unless she believes that agency contains elements that are not within the natural order. Borrowing from a suggestion from Russell we expanded the Nozick-Kane model of libertarian free agency and connected it to the Wignerian interpretation of quantum measurement. As such, free decisions and choices may well violate the Born rule of probability distribution and yet it is shown how such violations are unlikely to be detected in experiments. This model is probably the only model in which Loewer's van Inwagen style argument for the incompatibility between free agency and quantum indeterminism does not apply, and it is a model in which free agency is not only compatible but necessary. It is compatible with indeterminism and it is necessary for the determinateness of any measurement outcomes.